The objective of this research is to elucidate the in-depth mechanism of action of insecticides on the nerve membrane which is the most critical target site of a variety of insecticides. During the past eight years, we have been able to establish the basic approach, concept and techniques to study this problem, and the validity of this approach has been demonstrated for several insecticides. The techniques involve intracellular microelectrodes, voltage clamp and intracellular perfusion, and the ionic mechanism of action of insecticides on both axonal membranes and postsynaptic membranes can be studied. We now propose to extend this study in depth rather than horizontally. The effects of insecticides on ionic conductances of nerve membrane and postsynaptic membranes will be analyzed by means of voltage clamp techniques as a function of calcium concentration, pH and temperature. This approach is expected to lead to useful information as to the mechanism of the insecticide interaction with nerve membrane components. In order to identify the site of insecticide binding, the effects of treatment with proteases, phospholipases and certain protein reagents on the insecticidal action on the nerve membrane will also be explored. The structure-activity relationship of DDT and pyrethroids will be studied by comparing the effects on ionic conductances as a measure of activity. These experiments on the nerve membrane will provide the basis for the molecular mechanism of action of insecticides.